What is a dexamethasone suppression test ?

A dexamethasone suppression test can help a doctor learn the cause of a patient having high levels of the hormone cortisol. The doctor gives the patient dexamethasone, a synthetic version of cortisol, and checks the patient's urine to see how his or her body responds.

Why would a doctor recommend a dexamethasone suppression test ?

The test is often used when a doctor suspects that a patient has too many adrenal hormones, caused by a disorder such as Cushing's syndrome. The way a patient's cortisol levels respond to the test can tell a doctor if the problem is due to a pituitary tumor, or another cause.

What does a dexamethasone suppression test involve?

The test is done either as an overnight test, or over three days. Different types of the test use differing doses of dexamethasone.

In an overnight test, you will take a dose of dexamethasone by mouth at 11 p.m., and will have a blood sample drawn at 8 a.m. to measure the levels of cortisol in your blood.

In the three-day test, your doctor will have you collect your urine during the length of the test (as in the 24-hour urine collection test). Starting on the second day of the test, you will take a dose of dexamethasone by mouth every six hours for the next 48 hours.

Normally, a patient's cortisol levels will drop after taking dexamethasone. Laboratory analysis of the collected urine will help your doctor determine the cause of excess adrenal hormones.

How long is the recovery after a dexamethasone suppression test?

You can maintain your normal activities during the length of the test. The test has no recovery period.

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